Why cannot cite .tex @phdthesis citation?

I’m trying to cite a phdthesis report :

    documentclass[notitlepage]{article}

usepackage{amsmath, amssymb}
usepackage{pdflscape}
usepackage[left=0.3in,right=0.3in,top=0.3in,bottom=0.5in]{geometry}

usepackage{colortbl}
usepackage[margin=1cm]{caption}
usepackage{multirow}
usepackage{booktabs}
usepackage{float}
usepackage{graphicx}
graphicspath{{figures/}}

usepackage{longtable}

%usepackage{algorithm}

usepackage{algorithmic}

usepackage{pdfpages}
usepackage[ruled,vlined]{algorithm2e}
usepackage{ifoddpage}
usepackage{blindtext}
usepackage{authblk} 


 begin{filecontents}[overwrite]{references3.bib}

 

@phdthesis{hajjar2014cartes,
    title={Cartes auto-organisatrices pour la classification de donn{'e}es symboliques mixtes, de donn{'e}es de type intervalle et de donn{'e}es discr{'e}tis{'e}es.},
    author={Hajjar, Chantal},
    year={2014},
    school={Sup{'e}lec}
}

% ...........%
 end{filecontents}
renewenvironment{abstract}
{parnoindenttextbf{abstractname.} ignorespaces}
{parmedskip}


begin{document}

title{  title   }
author{author1 ,
    [email protected]  
}

affil[1]{Department of Computer Science,---------------------------- }


maketitle  


begin{abstract}
    small
    
some text .....................
    
    
end{abstract}

textbf{Keywords} : global numerical optimization, mono-objective, descent gradient variants, analytic hierarchy process,  hybrid optimization, random search

 
section{Problem formulation}
cite{hajjar2014cartes}  :

 


Floatbarrier


newpage

 
 

bibliographystyle{ieeetr}
bibliography{references3.bib}

end{document}

Using the previous script , i got the following output :

Unfortunately , the citation isn’t displayed as expected.

I hope my question is clear!

Thank you in advance for your help !